Are clot risks in the genes of cancer patients?

A new TREC study has looked into the role of genes on the risk of blood clots in cancer patients

Cancer is a common risk factor for developing blood clots (thrombosis), with up to 25% of all venous blood clots occurring in cancer patients. Also, family and twin studies have shown that almost two thirds of the blood clot risk is due to genetic factors. SNPs, pronounced “snips”, are mistakes made during the DNA copying process – almost like small single letter typos. In recent years several SNPs have been discovered that, if present, can increase a person’s risk for blood clots. We looked at the role of two SNPs (F5 rs6025 and F5 rs4524) on the risk of blood clots in cancer patients.

The participants of our study were recruited from the fourth and sixth surveys of the Tromsø Study. We conducted a case-cohort study that included 660 patients with a blood clot (cases) and 1793 subjects at the same age without a blood clot (sub-cohort). DNA was analyzed from blood samples to look for the presence of the two SNPs. We linked our data to the Cancer Registry of Norway and found that 461 of our study participants were diagnosed with cancer during the maximum 18-year study period.

We found that in people without cancer, these two SNPs increase the risk of blood clots. However, cancer patients with these SNPs had a much higher risk. In fact, these SNPs and cancer had a synergistic effect on the risk of blood clots. Synergy is when two components work together to produce an effect that is greater than the sum of their individual effects (like 1 + 1 = 3!). Cancer patients with these SNPs have a two- (F5 rs6025) and four-times (F5 rs4524) higher risk for blood clots than cancer patients without the SNPs.

We also found that the risk of blood clots in cancer patients with these SNPs increased mostly in the first half year after a cancer was diagnosed. This is probably because modalities to treat cancer, such as chemotherapy and surgery, put patients at a higher risk for blood clots and are normally started around this time. The presence of multiple simultaneous risk factors can put a patient at an especially high risk of blood clots. Since the risk of blood clots in these patients increases after a cancer diagnosis, in the future we could potentially test for these SNPs at the time of cancer diagnosis. This could help us identify cancer patients that are at an especially high risk of blood clots and potentially start those patients on preventative blood thinners (anti-coagulation), however, further studies in this field are needed.